#!/usr/bin/python3
"""
Write an iterator that iterates through a run-length encoded sequence.

The iterator is initialized by RLEIterator(int[] A), where A is a run-length
encoding of some sequence.  More specifically, for all even i, A[i] tells us the
number of times that the non-negative integer value A[i+1] is repeated in the
sequence.

The iterator supports one function: next(int n), which exhausts the next n
elements (n >= 1) and returns the last element exhausted in this way.  If there
is no element left to exhaust, next returns -1 instead.

For example, we start with A = [3,8,0,9,2,5], which is a run-length encoding of
the sequence [8,8,8,5,5].  This is because the sequence can be read as "three
eights, zero nines, two fives".

Example 1:

Input: ["RLEIterator","next","next","next","next"], [[[3,8,0,9,2,5]],[2],[1],
[1],[2]]
Output: [null,8,8,5,-1]
Explanation:
RLEIterator is initialized with RLEIterator([3,8,0,9,2,5]).
This maps to the sequence [8,8,8,5,5].
RLEIterator.next is then called 4 times:

.next(2) exhausts 2 terms of the sequence, returning 8.  The remaining sequence
is now [8, 5, 5].

.next(1) exhausts 1 term of the sequence, returning 8.  The remaining sequence
is now [5, 5].

.next(1) exhausts 1 term of the sequence, returning 5.  The remaining sequence
is now [5].

.next(2) exhausts 2 terms, returning -1.  This is because the first term
exhausted was 5,
but the second term did not exist.  Since the last term exhausted does not
exist, we return -1.

Note:

0 <= A.length <= 1000
A.length is an even integer.
0 <= A[i] <= 10^9
There are at most 1000 calls to RLEIterator.next(int n) per test case.
Each call to RLEIterator.next(int n) will have 1 <= n <= 10^9.
"""
from typing import List


class RLEIterator:
    def __init__(self, A: List[int]):
        """
        counter
        """
        self.cur_i = 0
        self.cur_used = 0
        self.A = A

    def next(self, n: int) -> int:
        run = self.cur_used + n
        while self.cur_i < len(self.A) and run > self.A[self.cur_i]:
            run -= self.A[self.cur_i]
            self.cur_i += 2

        if self.cur_i >= len(self.A):
            return -1

        self.cur_used = run
        return self.A[self.cur_i + 1]
